This study explores anaerobic/aerobic biodegradation efficiencies of aerobic
cometabolism with methanotrophs when contaminants trichloroethylene (TCE) and
cis-1,2-dichloroethylene (cDCE) are present individually or in tandem.
Methodology: Batch tests and an anaerobic/aerobic column system
were used to simulate saturated, contaminated aquifers. A brown glass bottle
with an effective volume of 44 m l-1 was prepared for the batch
test. An integrated one-dimensional sequential anaerobic/aerobic column
system was used to simulate the accumulative intermediates such as TCE, cDCE
and VC caused by incomplete degradation of PCE during the upgradient
anaerobic stage in the saturated aquifer. In the downgradient aquifer,
aerobic cometabolism was employed to degrade the intermediates. Methanotrophs
in the aerobic aquifer were inoculated to degrade the by-products of
incomplete degradation of PCE by aerobic cometabolism.
In the batch test, biodegradation of TCE was significantly inhibited by cDCE.
However, biodegradation of cDCE was not significantly inhibited by TCE. In
the simulated aquifer test, aerobic cometabolism completely degraded
intermediates (TCE, cDCE, and VC) produced by incomplete anaerobic degradation
of tetrachloroethylene (PCE). The results showed that methane, a by-product
of anaerobic reductive dechorination of PCE, was used as a primary substrate
for aerobic degradation, at a utilization rate of almost 100%.
Interpretation: Biodegradation of TCE was significantly
inhibited by cDCE. Bioremediation should have sufficient oxygen and methane
at aerobic stage to ensure that chlorinated ethenes fully mineralize.
Key words: Aerobic cometabolism, Anaerobic/aerobic
biodegradation, cis-1,2-dichloroethylene, Methanotrophs,Trichloroethylene